Fork and like trucks



Oct. 22, 1957 A. E. R. ARNOT 2,

FORK AND LIKE TRUCKS Filed May 12, 1955 5 Sheets-Sheet 1 IN'VENTOR Oct. 22, 1957 A. E. R. ARNOT FORK AND LIKE TRUCKS Filed May 12, 1955 3 Sheets-Sheet 2 Oct. 22, 1957 A. E. R. ARNOT FORK AND LIKE TRUCKS 3 Shee ts-Sheet 3 Filed May 12, 1955 IN VFN T R FORK AND LmE TRUCKS Alfred Erwin Reginald Arnot, Basingstoke, England, as-

signor to Emmanuel Kaye and John Reginald Sharp, both of Basingstoke, England Application May 12, 1955, Serial No. 507,966

Claims priority, application Great Britain May 13, 1954 6 Claims. or. 214-652) The present invention comprises improvements in or relating to industrial trucks of the type which have fork or other work engaging members carried by a rotatable head mounted on a carriage for up and down movement on a mast secured to the truck chassis. Hitherto such rotatable heads have been mounted in front of the mast and have taken up so much room as to materially increase the overhang of the forks in front of the wheel-base of the truck, which resulted in an increased tipping moment of the load on the truck. It is an object of the present invention to provide a construction which reduces the overhang of the forks, or other work engaging members, to a minimum.

According to the present invention a rotatable head for a truck of the type described is provided wherein the mast is of the kind comprising two uprights side-by-side, the carriage on the mast runs between the uprights, bracket means extend forwardly from the carriage to support a non-rotatable back-plate spaced from the mast, a rotatable plate for supporting the work-engaging members is mounted on the back-plate and carries a stem which passes through the back-plate to the rear thereof and means for rotating the stem are provided in the space between the back-plate and the mast.

In a preferred construction the bracket means comprise members secured to the back-plate near its upper edge, extending rearwardly therefrom between the sides of the mast and pivotally connected to the carriage about an axis which is located in or near the vertical plane containing the axis of the truck wheels, and wherein means are provided to exert tilting force on the back-plate about this axis. The means for rotating the stem may consist of a gear wheel on the stem behind the back-plate, a rack meshing with the pinion and jack cylinders in line with the rack and containing pistons to push it to and fro. The jack cylinders are preferably located horizontally above the gear-wheel and the gear-Wheel is of such size that the jack cylinder-axis is approximately at the same level as, and adjacent to, the pivotal axis of the brackets. This construction permits the largest possible jack cylinders to be used in the space provided, because the cylinder is positioned approximately level with the pivotal axis of the brackets and its movement is small, as being adjacent to the said axis, and has only a very small horizontal component.

The following is a description by way of example of one embodiment of this invention as applied to rotatinghead fork lift trucks.

In the accompanying drawings:

Figure 1 is a side elevation of the outline of a truck;

Figure 2 is a vertical section through the fork tilting and rotating mechanism of the truck shown in Figure 1, and

Figure 3 is a section upon the line 33 of Figure 2 locking in the direction of the arrows and with certain parts broken away to show the internal construction. The section upon which Figure 2 is taken is indicated by the arrows 2-2 in Figure 3.

States Pate t.

2,810,488 Patented Oct. 22, 1957 The truck shown in Figure 1 comprises a chassis 11 having a steerable power-driven rear-wheel 1 2 guided by a tiller-arm 13 and driving means located in a casing 14. Lateral ground wheels'15 are provided at the front of the chassis 11 and a mast 16 stands up from the chassis substantially in line with the axis of the wheels 15 and is supported by a stay 17. The mast 16 consists of two inwardly directed channel-section side-members which are united by a channel-section bottom-member 18 (Figure 2) and by a cross-member 19 at the top. On the mast there runs a carriage 20 which is provided with rollers 21, 22 to run inside the flanges of the channelmembers 16 which form the sides of the mast. The carriage supports forks 23 which are intended for lifting pallets or bales or the like, but for the forks there may be substituted any other device for holding goods, for example grippers for bales. The usual devices for raising and lowering the carriage 20 by means of a chain operated by an hydraulic cylinder located in the plane of the mast or just behind it are provided, but do not appear in the drawing, being well known. Instead of a non-extensible mast such as the mast 16 illustrated, the mast might have an extensible section running in the guides formed by the channel-shape side-members, and

the fork-carriage 20 might be mounted on the extensible section of the mast.

The carriage 20 comprises a front-plate 24 (Figure 2) with two rearwardly projecting side-plates 25, 2 6 welded to the back of the front plate at right-angles thereto and equally spaced apart on either side of the vertical centre line thereof, so as to fit within the mast side-members 1 6. A window 27 is formed in the carriage front-plate '24 near its top edge, between the side-plates, by cutting the metal away on three sides of the window and then bending the flap 28 so formed downwards and backwards at right-angles to the remainder of the front plate, within the side plates. The flap 28 is cut away in the middle and really forms two flaps of such dimensions that they lie just within the back-edges of the side-plates 25, 26, as shown in Figure 3. The bottom of the front plate 24, vertically in line with the flap 28 is bent rearwardly, at right angles to the front plate as shown at 29 Figure 2, so as to extend to a point just less than halfway within the side-plates. Transverse holes are drilled through the side-plates, above the flap 28, to pass stub axles 30 for the rollers 21, which axles are secured in place by nuts 32, the rollers 21 being carried on the axles 30 outside the carriage side-plates 25, 26. At the bottom of the side-plates 25, 26 there are other stub axles 33 which carry the rollers 22, and in this way the carriage runs freely up and down inside the channel-shape side-members16.

Strengthening plates 34 are welded to the upper sides of the top flap 28 at a point behind each top roller-axle to a point at the rear of the front plate 24 above the window 27 and is welded in this position. This portion of the front plate 24 above the window 27 is also "stiffened on its front side by a length of angle iron 35 which is welded horizontally thereon.

Pivotally mounted and spaced transversely apart on the topmost roller axles 30 are a pair of curved bracket members 36 which are welded at their outermost ends to a circular backplate 37 which forms non-rotatable support for the rotating head. The connection is stiffened bya cross-member 38, weldedon between the brackets 36. The circular back-plate 37 has an annular groove 39 on its front face near the edge, which groove aligns with a similar groove 40 in the back of a fork-carrying faceplate 41. Bearing balls 42 are arranged in the grooves and are held between the plates so that the back and face plates may rotate relatively to one another. Centrally positioned at the back of the face-plate 41 and extending rearwardly therefrom through an aperture at the centre of the back-plate 37, is a stem 43 provided with a spur gear 44 at its end, and rigidly bolted to the fork-carrying face-plate 41 by bolts 45. The rear of the back-plate 37 is provided with an annular groove 46, and the front of the spur gear 44 with a corresponding groove 47 and balls 48 are held in place therebetween. Thus the faceplate 41 and spur gear 44 can rotate freely, due to the balls 42, 48, on the back-plate 37. Above the spur gear 44, behind the back-plate 37 and adjacent to the topmost set of rollers 21, is a transversely extending hydraulic cylinder 50 which is cut away at its centre on its underside. comprises a piston rod 51 with a piston 52 at each end, the rod 51 being cut with rack teeth 54 which mesh with the spur gear 44. Fluid pressure connections through nipples 55 are made to each end of the cylinder so as to cause the rack 54 to be double acting. The length of the rack 54 is normally designed so as to be the equivalent of half the circumferential distance around the spur gear 44; therefore movement of the rack on full stroke in one direction causes the face-plate to rotate 180, say in a clockwise direction, and reversal of the pressure causes a return stroke of the rack 54 in the opposite direction, and anti-clockwise movement of the face plate 41.

The hydraulic cylinder 50 is attached by means of two split bearings 56, 57 to the rear of the back plate 37. Below the spur gear 44 and spaced apart equally either side of the centre line, a pair of short hydraulic ram cylinders 58 are pivotally mounted in brackets 59 on the carriage, which cylinders extend through apertures in plate 24 and contain rams 60 which act in a fore and aft direction parallel with the truck axis. Operation of the rams 60 against the back-plate 37 causes the plate to tilt forwardly or rearwardly on brackets 36 about the axis of the rollers 21. The curved arms 36 of the bracket members pass above, and clear of, the hydraulically operated rack cylinder 50 and as the cylinder 50 is positioned nearly on the level of and adjacent to the topmost pair of rollers 21, up and down tipping movement of the forks 23 is possible without appreciable movement of the cylinder 50 and it is possible to rotate the forks even when fully tilted. The cylinder 50 can be made large (because it is not necessary to allow clearance for horizontal movements) without necessitating undue overhang of face plate 37 from the mast 16.

The window construction 27 allows a space into which the rack cylinder 50 and bracket members 36 may enter on the upward and downward tilting of the head.

In the hydraulic connections to the jack cylinder 50 there should be incorporated a flow-restriction device shown at which limits the rate of flow of fluid to the jack. In case heavy loads with a centre of gravity markedly out of centre with the jack are being handled, this prevents the load taking control should the centre of gravity reach a position to one side of the central pivot 43 where it assists jack movement. Otherwise the rotation might be too rapid under these circumstances.

The forks 23 are hooked on the face-plate 41 as shown and are limited by stops 63 secured to the front of the face-plate between them, so that when they are as close together as the stops permit, their overall width is approximately equal to the width of entry to the load. This ensures that the stops take the load and that there is no risk that the forks might slide oil the carriage as soon as it has turned through The spur gear 54 is enclosed by a casing 64. The carriage 22 is prevented from lateral play by additional rollers 61 on brackets 62 secured to the side-plates 25, 26 of the carriage.

Within the cylinder is a piston assembly which The hydraulic connections may be carried to the jack which rotates the head by a flexible connection such as is described in British patent application No. 8529/54.

I claim:

1. In a truck of the type described, a mast comprising a pair of generally upright members, a carriage movable along said mast, plate means for supporting work engaging members mounted on said carriage for rotation about a generally horizontal axis, said plate means being supported on said carriage for pivotal movement about a horizontal axis at right angles to the axis of rotation of said plate means, means for rotating said plate means about its axis of rotation including pinion means mounted on said rotatable plate means, and rack means engaging said pinion means for rotating said pinion means, said rack means including fluid actuated piston and cylinder means at opposite ends thereof providing double acting means for rotating said rotatable plate, and means for tilting said plate about its pivot axis.

2. A truck as claimed in claim 1, wherein the carriage takes the form of a front plate having two rearwardly projecting side plates secured to it on which are mounted stub axles for guide rollers on the carriage and wherein the front plate of the carriage has an opening cut in it through which extend bracket means supported on the axles of the upper rollers and carrying the back-plate.

3. A truck as claimed in claim 1, wherein the rotatable plate for supporting the work-engaging-members is connected to the back-plate by ball bearings.

4. A truck as claimed in claim 1 wherein a restriction is provided in the fluid pressure supply to said piston and cylinder means.

5. In a truck of the type described, a mast comprising a pair of generally upright members, a carriage movable along said mast, work engaging member supporting means mounted on said carriage for rotation about a generally horizontal axis, and means for rotating said supporting means about its axis of rotation including pinion means mounted on said supporting means, and a single transversely extending rack engaging said pinion means for rotating said pinion'means, said rack being mounted on said carriage and including fluid actuated piston and cylinder means at opposite ends thereof providing double acting means for rotating said supporting means.

6. In a truck of the type described, a mast comprising a pair of generally upright members, a carriage movable along said mast and having bracket means extending forwardly thereof, fixed plate means supported by said bracket means for pivotal movement about a transverse horizontal axis, means for tilting said fixed plate about its pivot axis, rotatable plate means for supporting work engaging members and mounted on said fixed plate means for rotation about a generally horizontal longitudinal axis, means for rotating said rotatable plate means about its axis of rotation including pinion means mounted on said rotatable plate means, and rack means engaging said pinion means for rotating said pinion means through an angle of at least from a central position, said rack means being mounted on said fixed plate means and including transversely extending piston and cylinder means at opposite ends thereof providing double acting means for rotating said rotatable plate through a total movement of at least 360".

References Cited in the file of this patent UNITED STATES PATENTS 2,281,004 Lehmann et al Apr. 28, 1942 2,595,131 Ehmann Apr. 29, 1952 2,604,220 Frischmann July 22, 1952 2,609,114 Backofen et al. Sept. 2, 1952 

